JP4080408B2 - Battery protection IC and battery pack using the same - Google Patents

Description

  The present invention relates to a protection IC for detecting an abnormal state of a secondary battery, for example, a lithium ion secondary battery, and more particularly to a battery protection IC that provides a charge / discharge protection function for a battery pack in which a plurality of batteries are connected in series. Battery pack.

  2. Description of the Related Art In recent years, secondary batteries are used as power sources for portable electronic devices whose demand is rapidly increasing. Among secondary batteries, lithium ion secondary batteries are mainstream because they are lightweight and have a high energy density. Since the secondary battery deteriorates due to overcharge, overdischarge, etc., a protection circuit for protecting the secondary battery from overcharge or overdischarge is used. Since lithium ion secondary batteries are particularly vulnerable to overcharge and overdischarge, it is essential to provide a protective circuit in many cases.

  Among portable electronic devices, battery packs in which modules in which a plurality of batteries are connected in series are connected in parallel are used for notebook computers and the like. When a lithium ion secondary battery is used for the battery pack, it is necessary to monitor all batteries connected in series with a protection circuit. Since most notebook PCs are equipped with four battery packs (a battery pack in which four batteries are connected in series), a four-line protection IC with a protection circuit for monitoring each of the four batteries is commercially available. Has been.

On the other hand, a versatile battery pack suitable for electronic devices other than notebook computers has also been proposed (see, for example, Patent Document 1). Here, it is proposed that a protection circuit is connected in parallel to each of a plurality of batteries connected in series to protect the battery from overcharge and overdischarge.
JP 2000-354335 A

  According to the proposal of Patent Document 1, a photocoupler and FET (field effect transistor) for integrating outputs from the protection circuits of all the batteries are required. Therefore, there is a problem that the circuit structure becomes complicated and the cost increases. In addition, multi-straight protection ICs that are available as general-purpose products are usually for 4-straight use, and if you want to provide protection ICs in a battery pack in which many batteries are connected in series, you need to obtain a custom-made product. Costs are getting higher and higher.

  The present invention has been made in view of such a situation, and a main object of the present invention is to provide a multiple protection IC that can cope with any number of batteries connected in series.

  The battery protection IC of the present invention is a multi-battery battery protection IC that monitors a block composed of a plurality of batteries connected in series. The protection IC monitors (a) the voltage of each battery in the block. (B) an output terminal A for outputting a signal output from the detection circuit to the outside, (c) a connection terminal B for connection to another protection IC having the same function as the protection IC, and (d ) An output circuit for connecting the output terminal A and the connection terminal B is provided, and the output circuit is electrically connected between the output terminal A and the connection terminal B according to the output of the detection circuit. The present invention relates to a protection IC that has a function of changing a state and a function of transmitting a signal input from the another protection IC to the connection terminal B to the output terminal A, and is capable of cascade connection.

  Conventional protection ICs could not be cascade-connected, but the protection IC of the present invention includes an output circuit having a predetermined function, an output terminal, and a connection terminal. Any number of four direct battery protection ICs can be cascade-connected. When the detection circuit detects any abnormality of the battery being monitored, the electrical state between the output terminal and the connection terminal changes in the protection IC having the detection circuit. The change is output as a signal from the output terminal A, and when the output terminal is cascade-connected to the connection terminal B of another protection IC, the change is transmitted there. Then, the signal input to the connection terminal B of another protection IC is transmitted to the output terminal A of the protection IC. With such a function, it is possible to detect an abnormality wherever an abnormality occurs in batteries connected in series.

  According to the present invention, in the two protection ICs, the output terminal A of one protection IC is connected to the connection terminal B of the other protection IC, or the connection terminal B of one protection IC is connected to the other protection IC. The present invention relates to a method of using a protection IC that cascades two protection ICs by connecting to an input terminal A and monitors the voltage of each battery in the two blocks.

  According to the present invention, in the three or more protection ICs, the output terminal A and the connection terminal B of one protection IC are connected to the connection terminal B of another protection IC and the input terminal A of another protection IC, respectively. The present invention relates to a method of using a protection IC in which three or more protection ICs are cascade-connected by configuring one or more patterns to monitor the voltage of each battery in the three or more blocks.

Oite The present onset bright, the output circuit includes a current source and the transistor, the current source, the output of the detection circuit, is turned on or off, the current output of the current source is directly to the output terminal One of the source and drain of the transistor is connected to the output terminal, and the other is connected to the connection terminal.

  According to such a configuration, in the normal state, all the terminals of the cascade-connected protection ICs can be turned off, and all the current sources can be turned off. When the detection circuit detects any abnormality of the battery being monitored, the output terminal A is turned on by turning on the current source of the protection IC having the detection circuit. The ON signal is transmitted to the output terminal A when the output terminal is cascade-connected to the connection terminal B of another protection IC, turns on the downstream transistor, and is connected to the source or drain of the transistor. Turn on. In this way, the ON signal is sequentially transmitted to the downstream protection IC. Therefore, the above abnormality can be detected at the terminal terminal.

  In another aspect of the present invention, the output circuit includes a switch element that is turned off by the output of the detection circuit, and one terminal of the switch element is connected to the output terminal. The terminal is connected to the connection terminal.

  According to such a configuration, in the normal state, all the terminals of the cascade-connected protection ICs can be turned on, and a slight current flows through any of the terminals. When the detection circuit detects any abnormality of the battery being monitored, all the terminals of the cascaded protection ICs are turned off by turning off the switch element of the protection IC having the detection circuit. The above-mentioned abnormality can be detected. Such a configuration is excellent in reliability because an abnormality can be detected even when the protection IC generates a failure such as disconnection between terminals.

  The detection circuit includes, for example, (a) a charge detection circuit that detects that at least one of the monitored battery voltages has reached a charge switching voltage, and (b) at least one of the monitored battery voltages has reached an overcharge voltage. And (c) at least one selected from the group consisting of overdischarge detection circuits for detecting that at least one of the monitored battery voltages has reached the overdischarge voltage. That is, the protection IC may be a single function protection IC having one detection function, or may be a multi-function protection IC having a plurality of detection functions.

  The present invention further includes a multi-cell battery pack comprising four or more batteries connected in series and a plurality of cascaded multi-battery protection ICs for monitoring them, wherein the four or more batteries connected in series are connected. The battery is divided into a plurality of blocks, and one protection IC is installed for each block. Each protection IC includes: (a) a detection circuit that monitors the voltage of each battery in the block; (b) An output terminal A for outputting a signal output from the detection circuit to the outside; (c) a connection terminal B for connection to another protection IC selected from the plurality of protection ICs; and (d) a connection to the output terminal A. An output circuit for connecting to the terminal B, the output circuit having a function of changing an electrical state between the output terminal A and the connection terminal B in accordance with an output of the detection circuit; Along with said another protection The signal input to the connection terminal B from C to a multi-linear battery pack having a function of transmitting to the output terminal A.

  According to the multi-battery battery protection IC of the present invention, each battery in a block made up of a plurality of batteries connected in series and each battery in all other blocks connected in series with the block are overcharged. Overdischarge and the like can be detected.

  Since the number of protection ICs connected in cascade is not limited, a protection circuit can be configured with a simple configuration regardless of how many batteries are connected in series. The process voltage of the protection IC may be a value obtained by adding a slight margin to the sum of the battery voltages in the block monitored by the protection IC, and the total voltage of the batteries connected in series may exceed the process voltage of the protection IC. Absent.

  The output circuit has a current source and a transistor, the current source is turned on or off by the output of the detection circuit, the current output of the current source is directly transmitted to the output terminal, and one of the source and drain of the transistor is connected to the output terminal and the other Is connected to the connection terminal, it suffices to pass a current through the protection IC only when an abnormality is detected, so that a protection circuit excellent in energy saving can be configured.

  The output circuit has a switch element that is turned off by the output of the detection circuit, one terminal of the switch element is connected to the output terminal, and another terminal is connected to the connection terminal. In addition to the case where an abnormality occurs in the battery being monitored, each terminal is turned off even when a failure occurs in the protection IC, so that the abnormality can be detected. Excellent in properties.

  In the multiple battery pack of the present invention, since the protection circuit is configured by cascading the same kind of protection ICs, the configuration of the battery pack is simplified. Further, if the protection IC is standardized, the cost can be greatly reduced. In addition, it is possible to configure a battery pack having a total voltage equal to or higher than the process breakdown voltage of the protection IC.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
FIG. 1 shows an example of a multiple battery pack (battery pack 36a) including a plurality of batteries 1a to 1i connected in series and protection ICs 30a to 30c. In the protection ICs 30a and 30b, a part of the circuit structure is omitted, but the protection ICs 30a, 30b, and 30c all have the same function.

  The batteries 1a to 1i are connected in series, and one block is formed for every three batteries. One protection IC is installed in each block, the protection IC 30a monitors the batteries 1a to 1c, the protection IC 30b monitors the batteries 1d to 1f, and the protection IC 30c monitors the batteries 1g to 1i.

  Each protection IC includes an overvoltage detection circuit 34 that detects that any battery in the block in which it is installed has reached overcharge, and an overdischarge detection that detects that any battery has reached overdischarge. Circuit 35. The overvoltage detection circuit 34 monitors the terminal voltage of each battery when the battery pack is charged, and outputs an overvoltage signal when the terminal voltage of any battery becomes equal to or higher than a specified value. The overdischarge detection circuit 35 monitors the terminal voltage of each battery when the battery pack is discharged, and outputs an overdischarge signal when the terminal voltage of any of the batteries becomes a specified value or less.

  The switch 71 for reporting an overvoltage signal and the switch 72 for reporting an overdischarge signal are off in a normal state, and are turned on when an overvoltage signal or an overdischarge signal is detected. The overvoltage signal is transmitted to the output terminal 16 by turning on the switch 71 and causing the current source 61 and the output terminal 16 to conduct. Further, the overdischarge signal is transmitted to the output terminal 15 by turning on the switch 72 and making the current source 62 and the output terminal 15 conductive.

  Output terminals 15 and 16 are connected to connection terminals 25 and 26 via FETs 55 and 56, respectively. However, in protection IC 30c, connection terminals 25 and 26 are not connected anywhere, and FETs 55 and 56 operate. There is nothing. That is, the connection terminal of the protection IC 30 that monitors the block composed of the batteries having the highest potential among the plurality of batteries connected in series is not connected anywhere.

  On the other hand, the output terminals 15 and 16 are connected to the connection terminals 23 and 24 of the protection IC 30b adjacent to the protection IC 30c, respectively. The connection terminals 23 and 24 are connected to the output terminals 13 and 14 via FETs 53 and 54, respectively. Similarly, the output terminals 13 and 14 of the protection IC 30b are connected to the connection terminals 21 and 22 of the protection IC 30a adjacent to the protection IC 30b, respectively. The connection terminals 21 and 22 are connected to the output terminals 11 and 12 via FETs 51 and 52, respectively.

  Since each FET has a function of transmitting a signal input to the connection terminal to the output terminal, the overvoltage signal or the overdischarge signal output from any of the protection ICs is finally output from the output terminal 11 and the protection IC 30a. 12 and pulled down by resistors 81 and 82, and then output to monitor output terminals 42 and 43 of the battery pack.

  The overvoltage signal transmitted to the monitoring output terminal 43 controls the charger during charging. That is, the charger can detect the end timing of charging or the switching timing of the charging mode based on the overvoltage signal, so that appropriate charging can be performed. Further, the overdischarge signal transmitted to the monitoring output terminal 42 controls the device connected to the battery pack 36 at the time of discharging. That is, since the device can know that the battery capacity has decreased to a predetermined amount by the overdischarge signal, it can immediately shift to the end mode.

Next, the functions of the FETs 52, 54, and 56 will be described in detail.
The FET 56 is always off because the connection terminal 26 is not connected anywhere. Furthermore, if the switch 71 is off, the output terminal 16 is in an off state where no current or voltage is applied and the potential is not determined. Normally, a parasitic diode is generated at each terminal of the IC with respect to the lowest potential of the IC. Therefore, the potential of the output terminal 16 does not become lower than the potential lower than the lowest potential of the protection IC 30c by Vbe.

  Since the connection terminal 24 is connected to the output terminal 16 of the protection IC 30c, the FET 54 is off unless the potential of the output terminal 16 is higher than the gate potential of the FET 54 by 1V or more. At this time, the gate potential of the FET 54 is the power supply potential of the protection IC 30b, which is the ground potential of the protection IC 30c. Therefore, the output terminal 14 of the protection IC 30b is also turned off. Similarly, the FET 52 of the protection IC 30a is turned off, and the potential of the output terminal 12 is pulled down by a resistor to the ground potential.

  In this state, when the switch 71 is turned on, the FET 56 remains off, but the potential of the output terminal 16 rises because the specified current of the current source 61 tends to flow. Finally, the potential of the output terminal 16 becomes a potential sufficient to turn on the FET 54, that is, a potential higher by about 1V than the power supply potential of the protection IC 30b.

  As a result, the FET 54 inside the protection IC 30b becomes conductive, and the potential of the output terminal 14 rises as the current of the current source 61 starts to flow to the output terminal 14. As a result, the potential at which the FET 52 is turned on, that is, a potential higher by about 1 V than the power supply potential of the protection IC 30a.

  As described above, the current flowing out from the current source 61 of the protection IC 30c flows out to the output terminal 12 via the FET 54 and the FET 52, and flows through the resistor to generate a resistance value × current value voltage.

The FETs 51, 53, and 55 operate in the same manner as described above.
The voltage applied to the connection terminals of the protection ICs 30a and 30b is up to about 1V higher than the power supply voltage of each IC, and the withstand voltage of each IC only needs to be 1V or more higher than the total voltage of the batteries that each IC is responsible for monitoring. . For example, since the batteries monitored by the protection IC 30c are the batteries 1g to 1i, the power supply voltage of the protection IC 30c is a series voltage of the batteries 1g to 1i, and the withstand voltage of the protection IC 30c may be a value obtained by adding about 1V thereto. .

  When the battery pack is being charged, current flows from the external terminal 44 of the battery pack, and the terminal voltage of each of the batteries 1a to 1i connected in series gradually increases. Although it is desired that the performance of the batteries 1a to 1i be as uniform as possible, there is usually a variation in performance due to slight initial variation, temperature imbalance, difference in deterioration amount, and the like.

  In the case of a lithium ion secondary battery, if the voltage of only one battery rises and becomes overcharged, the battery may be deteriorated or may become dangerous. For this reason, it is necessary to individually check the voltages of all the batteries and to terminate the charging or switch the charging mode when the voltage of any battery reaches a specified level.

  If the voltage of the battery 1h reaches a specified level, the overvoltage detection circuit 34 detects this and the switch 71 is turned on. The current from the current source 61 is input from the output terminal 16 to the connection terminal 24, output to the output terminal 14 via the FET 54, and flows out from the connection terminal 22 to the output terminal 12 via the FET 52. As a result, the monitoring output terminal 43 becomes H level. Even if any voltage of the batteries 1a to 1i increases, the monitoring output terminal 43 can be set to the H level by the same principle.

  Next, when the battery pack is being discharged, current is discharged from the external terminal 44. And the overdischarge detection circuit 35 detects the battery which fell below the voltage of the regulation level first among the batteries 1a to 1i, the current flows in the same operation as at the time of charging, and the monitoring output 42 becomes H.

<< Embodiment 2 >>
FIG. 2 shows an example of the circuit configuration of FIG. 1 more specifically. For simplicity of explanation, only the overvoltage detection circuit is illustrated, but the overdischarge detection circuit can be configured in the same manner.

  An overvoltage detection circuit 34a provided inside the protection IC 30a checks the terminal voltage of each of the batteries 1a to 1c. When the voltage of any battery reaches a specified level, the FET 73 is turned on. The FET 73 is connected to the current source 63 via the resistor 83. The current source 63 is composed of a current mirror circuit composed of two P-type FETs, and constitutes a current source by mirroring the current flowing through the resistor 83 at a constant ratio when the FET 73 is turned on.

  When FET 73 is off, the current through resistor 83 is zero and the mirrored current is also zero. Therefore, the current source 63 can be turned on and off by turning the FET 73 on and off, and the current output flowing to the output terminal 11 can be turned on and off.

<< Embodiment 3 >>
FIG. 3 shows another embodiment of the protection IC. Here, only the overvoltage detection circuit is illustrated for the sake of simplicity of explanation, but the overdischarge detection circuit can be configured in the same manner. The protection IC 31c has a part of the circuit structure omitted, but the protection ICs 31a, 31b and 31c all have the same function. However, unlike the protection ICs 31a and 31b, the bias output terminal 29 of the protection IC 31c responsible for the uppermost block of batteries connected in series is open.

  The drain and source of the FET 53 included in the protection IC 31b are connected to the connection terminal 23 and the output terminal 13 via resistors 84 and 85, respectively. The gate of the FET 53 is connected to the maximum potential point of the protection IC 31c in the first embodiment, but is connected to an intermediate potential point determined by the resistors 87 and 88 in the present embodiment. This intermediate potential is necessary only for the protection IC 31c positioned at the highest level. In the battery protection ICs 31a and 31b connected to the lower order of the protection IC 31c, the bias output terminals 27 and 28 are short-circuited to the power supply potential point of their ICs. The Therefore, the gates of the FETs 51 and 53 become the power supply potential of their ICs.

Next, the operation of the lower protection IC will be described taking the protection IC 31b as an example.
In the protection IC 31b, an FET 76 that short-circuits the gate and drain of the FET 53 is provided to turn the FET 53 on and off. The FET 76 is turned on and off by the FET 74. A resistor 86 is provided between the gate and drain of the FET 76, and the FET 76 is completely turned off when the FET 74 is off.

  Under normal conditions, the FETs 51, 53 and 55 are all in an on state, and a current always flows into the resistor 81 connected to the output terminal 11. Here, for example, when the overvoltage detection circuit 34a ′ or 34b ′ detects any abnormality of the batteries 1a to 1f, the FET 73 or 74 is turned off, and the FET 51 or 53 is turned off, current flows into the resistor 81. The monitoring output terminal 42 becomes L level.

<< Embodiment 4 >>
The battery pack 36d of FIG. 4 includes the protection ICs 32a to 32c as described in the third embodiment in which the output terminals 11 and 12 are in the on state in the normal state, and further includes the FET 58 and the output terminal driven by the output terminal 12. 11 is provided. The source and drain of the FETs 57 and 58 are short-circuited by protective diodes 59 and 60, respectively. If any of the battery voltages becomes higher than a specified level during charging, the terminal 12 becomes L level, the FET 58 is turned off, and charging is stopped. On the other hand, if any battery voltage becomes lower than the specified level during discharge, the terminal 11 becomes L level, the FET 57 is turned off, and the discharge stops.

  According to such a configuration, when an abnormality occurs in the external charger and charging cannot be stopped, or when forcible charging is attempted using a charger other than the specified one, before the battery enters a dangerous state. In addition, the charge can be cut by itself. Similarly, overdischarge that causes deterioration of the battery during discharge can be prevented by its own power.

  As described above, the protection IC of the present invention and the battery pack using the protection IC include all the batteries in the block composed of a plurality of batteries connected in series and all the batteries in the other blocks connected in series with the block. The overcharge / discharge detection for the battery can be detected. Further, since there is no limit on the number of cascaded protection ICs, a protection circuit can be formed with a simple configuration for any battery pack including any number of batteries. Therefore, the present invention is useful as a protection mechanism for detecting an abnormal state of a secondary battery, for example, a lithium ion secondary battery.

It is a circuit diagram concerning Embodiment 1 of the present invention. It is a circuit diagram concerning Embodiment 2 of the present invention. It is a circuit diagram concerning Embodiment 3 of the present invention. It is a circuit diagram concerning Embodiment 4 of the present invention.

Explanation of symbols

1a to 1i batteries 11 to 16 output terminals 21 to 26 connection terminals 27, 28, and 29 bias output terminals 30a, 30b, and 30c protection ICs
31a, 31b, 31c Protection IC
32a, 32b, 32c Protection IC
34a, 34a ', 34b', 34c Overvoltage detection circuit 35c Overdischarge detection circuit 36a, 36b, 36c, 36d Battery pack 41, 44 External terminal 42, 43 Monitoring output terminal 51-56, 73-76 FET
57, 58 FET
59, 60 Protection diode 61, 62, 63 Current source 71, 72 Switch 81-88 Resistance

Claims (6)

A multi-battery battery protection IC that monitors a block of a plurality of batteries connected in series,
The protective IC is
(A) a detection circuit for monitoring the voltage of each battery in the block;
(B) an output terminal A for outputting a signal output from the detection circuit to the outside;
(C) a connection terminal B for connecting to another protection IC having the same function as the protection IC, and (d) an output circuit for connecting between the output terminal A and the connection terminal B.
The output circuit which has a current source and the transistor, according to an output of the detection circuit, electrical state alters function between the connection terminal B and the output terminal A, and from the another protection IC A function of transmitting a signal input to the connection terminal B to the output terminal A;
The current source is turned on or off by the output of the detection circuit,
The current output of the current source is directly transmitted to the output terminal,
A protection IC in which one of a source and a drain of the transistor is connected to the output terminal and the other is connected to the connection terminal, and cascade connection is possible.   In the two protection ICs, the output terminal A of one protection IC is connected to the connection terminal B of the other protection IC, or the connection terminal B of one protection IC is connected to the input terminal A of the other protection IC. 2. The method of using a protection IC according to claim 1, wherein two protection ICs are connected in cascade to monitor the voltage of each battery in the two blocks.   In the three or more protection ICs, one or more patterns connecting the output terminal A and the connection terminal B of one protection IC to the connection terminal B of another protection IC and the input terminal A of another protection IC, respectively. 3. The method of using a protection IC according to claim 1, wherein three or more protection ICs are cascaded to constitute a configuration and the voltage of each battery in the three or more blocks is monitored.   The output circuit has a switch element that is turned off by the output of the detection circuit, one terminal of the switch element is connected to the output terminal, and another terminal is connected to the connection terminal. The protection IC according to claim 1. The detection circuit includes:
(A) a charge detection circuit for detecting that at least one of the monitored battery voltages has reached a charge switching voltage;
(B) an overcharge detection circuit that detects that at least one of the monitored battery voltages has reached an overcharge voltage; and (c) an overdischarge that detects that at least one of the monitored battery voltages has reached an overdischarge voltage. The protection IC according to claim 1, further comprising at least one selected from the group consisting of detection circuits. A multi-cell battery pack comprising four or more batteries connected in series and a plurality of cascaded multi-cell battery protection ICs for monitoring them,
The four or more batteries connected in series are divided into a plurality of blocks, and one protection IC is installed for each block.
Each protection IC
(A) a detection circuit for monitoring the voltage of each battery in the block;
(B) an output terminal A for outputting a signal output from the detection circuit to the outside;
(C) a connection terminal B for connecting to another protection IC selected from the plurality of protection ICs, and (d) an output circuit for connecting the output terminal A and the connection terminal B.
The output circuit which has a current source and the transistor, according to an output of the detection circuit, electrical state alters function between the connection terminal B and the output terminal A, and from the another protection IC A function of transmitting a signal input to the connection terminal B to the output terminal A;
The current source is turned on or off by the output of the detection circuit,
The current output of the current source is directly transmitted to the output terminal,
A multiple battery pack in which one of a source and a drain of the transistor is connected to the output terminal and the other is connected to the connection terminal .

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